Bacterial DNA can be found in the synovial fluid of some types of arthritis patients. CpG motifs in bacterial DNA (CpG DNA) induce leukocytes to express various pro-inflammatory mediators and cytokines such as TNF-alpha, IL-6, COX-2, and PGE2 which have been implicated in arthritis. Indeed, it has been demonstrated that CpG DNA induces arthritis in an experimental setting. CpG DNA activates NF-kappaB and Mitogen activated protein kinases (MAPKs) through a TLR9/MyD88- dependent pathway. NF-kappaB and MAPKs play as critical role in the CpG DNA-induced pro-inflammatory cytokine production and COX-2 expression. Interestingly, our preliminary data demonstrated that CpG DNA activates protein kinase C (PKC) isoenzymes whose activity is essential for the CpG DNA-mediated MAPK activation and cytokine production. The goal of this study is to understand the role of protein kinase C (PKC) in the CpG DNA-mediated pro-inflammatory reaction. To approach this goal, we will identify isoforms of PKC activated by CpG DNA and investigate biologic role of PKC in the CpG DNA- induced pro-inflammatory cytokine production and COX-2 expression. PKC isoforms activated by CpG DNA in macrophages will be identified by performing isotype-specific PKC assay. To investigate biologic role of PKC isozymes, dominant active and dominant negative PKC isoforms will be introduced into RAW264.7 cells. These mutant cells will be analyzed by flow cytometry, electrophoretic mobility shift assay, Real- time PCR, in vitro kinase assay, western blot, ELISA and confocal microscopy. If time allowed, candidate upstream regulators of PKC in the CpG DNA-mediated signaling pathway will also be investigated.